COVID-19: Single-use N95 respirators can be used again after decontamination, study says

N95 respirators, which are widely worn by health care workers treating COVID-19 patients, and are designed to be used only once, can be decontaminated effectively and worn up to three times, according to a new study that could help reuse these scarce resources amidst the pandemic.

Researchers, including those from The University of California Los Angeles (UCLA) in the US, said N95 respirators reduce exposure to airborne infectious agents, including the novel coronavirus, SARS-CoV-2, and are one of the key pieces of personal protective equipment used by clinical workers in preventing the spread of COVID-19.

The study, published in the journal Emerging Infectious Diseases, noted that critical shortages of these masks have driven efforts to find new decontamination methods that can extend their use.

"Although N95 respirators are designed for just one use before disposal, in times of shortage, N95 respirators can be decontaminated and reused up to three times," said study co-author James Lloyd-Smith from UCLA.

"But the integrity of the respirator's fit and seal must be maintained," Lloyd-Smith added.

In the study, the scientists tested several decontamination methods on small sections of N95 filter fabric that had been exposed to the virus, including the use of vaporised hydrogen peroxide, dry heat at 70 degrees Celsius, ultraviolet light (UV), and a 70 per cent ethanol spray.

According to the researchers, all four methods eliminated detectable viable virus from the N95 fabric test samples.

The scientists then treated fully intact, clean respirators with the same decontamination methods to test their reuse durability, following which volunteered to wear the masks for two hours to determine if they maintained a proper fit and seal over the face.

They decontaminated each mask three times, using the same procedure with each.

According to the study, masks treated with vaporized hydrogen peroxide experienced no failures, suggesting they potentially could be reused three times.

Those treated with UV light and dry heat began showing fit and seal problems after three decontaminations, the researchers said, indicating these respirators potentially could be reused twice.

They concluded that vaporized hydrogen peroxide was the most effective method because no traces of the virus could be detected after only a 10-minute treatment.

Based on the findings, the scientists said UV light and dry heat are also acceptable decontamination procedures, as long as the methods are applied for at least 60 minutes.

The ethanol spray, however, damaged the integrity of the respirator's fit and seal after two sessions, and they do not recommend it for decontaminating N95 respirators.

According to the researchers, people decontaminating an N95 respirator should closely check the fit and seal over the face before each reuse.